Laser Module And System

ABSTRACT

Laser modules and systems are provided that are smaller, lighter, and less complex and while more reliably generating collimated laser beams having limited divergence.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/894,711 filed Oct. 23, 2013.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to solid state laser modules and lasersystems that incorporate solid state laser modules.

Description of Related Art

Laser devices that incorporate solid state laser modules are used for avariety of purposes including but not limited to applications such astarget marking, pointing, designating, aiming, data communication, andstand-off spectral analysis. These applications require laser systemsthat are capable of directing laser beam through free space to create alaser spot on a distant target that reflects enough light to be observedor sensed by an electronic sensor such as a spectrometer, aspectrophotometer or an array type image sensor that may itself be agreat distance from the target. To accomplish this, it is necessary toprovide a laser beam that forms a spot of laser light on the distanttarget having at least a minimum intensity. Such applications require alaser system that can emit a laser beam with limited divergence.

In many of these applications, it is also necessary that such laserdevices are in a form that is easily transported to a point of use andthat can be readily and reliably operated when needed. This requireslaser devices that are lighter, have a smaller cross-sectional area andreduced volume while still being robust enough to operate after beingexposed to vibration, tension, compression, bending forces, torsionalloads, and environmental extremes during transport and use. It isparticularly important in military, homeland security, first responderapplications that such laser devices will remain operational even whenexposed to high levels of shock.

However, it is challenging to design and assemble smaller laser devices.In part this is because the natural inclination of engineers andscientists is to achieve size reduction through the simple expedient ofdownscaling extent designs and processes. However, in the field of lasertechnology simply using smaller versions of components to achieve systemsize reductions rarely achieves reliable results.

An example of the complications that can arise when seeking to downsizelaser systems through downscaling components can be illustrated withreference to U.S. Pat. No. 7,492,806, entitled “Compact Mid-IR Laser”which describes what is known in the art as a high heat load lasermodule.

FIG. 1 shows an exploded isometric view adapted from FIG. 2A of the '806patent. FIG. 2 shows generally a front elevation view of such a highheat load laser module. As can be seen in FIG. 1, high heat load lasermodule 10 has a housing 12 that can be on the order of 3 cm×4 cm×6 cm.Housing 12 contains a quantum cascade laser 14 that emits infraredlight, a submount 16 on which quantum cascade laser 14 sits. A heatspreader 18 has a keyway 20 within which submount 16 is mounted. Housing12 also contains drive circuitry 24, a thermoelectric cooling system 26,a lens 28 and conductors 30 that extend through sidewalls of sealed box12 to supply electrical energy and control signals to drive circuitry24, a thermoelectric cooling system 26 and quantum cascade laser 14.

Box 12 is comprises a front wall 32 with an opening 34 and a window 36,a lid 38, a base 40 and a rear wall 48. Heat spreader 18 is positionedso that quantum cascade laser 14 directs divergent infrared light towardwindow 36. Lens 28 is positioned between quantum cascade laser 12 andwindow 36 to collect infrared light emitted by quantum cascade laser 14and to focus this light.

The '806 patent uses a small focal length lens and asserts that “thesmall focal length of the lens is important in order to realize a smalloverall footprint of the laser device.” The lens 28 “may comprise anaspherical lens with a diameter approximately equal to or less than 10mm and preferably approximately equal to or less than 5 mm. Thus, thefocal length may be one of approximately 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 mm and any fractional valuesthereof. The focal length of the lens [28] is fabricated to beapproximately ½ the size of the diameter. Thus, 10 mm diameter lens willhave a focal length of approximately 5 mm, and a 5 mm diameter lens willhave a focal length of approximately 2.5 mm.

Similarly, the importance of using a small or short focal length lens toprovide smaller sized laser systems has been described in other patentsincluding U.S. Pat. No. 7,535,656, filed on Sep. 22, 2006 which definesa the term short focal length lens as referring “to lenses and focusingmirrors which have a focal length less than about 8 millimeters. Asthere is no certain meaning associated with a lens having f=0, wedeclare a lower limit on our ‘short focal length’ to be about 0.5millimeters. Any value between 0.5 and 8 millimeters is hereinconsidered a short focal length.”

However, the design decision to use a small or short focal length lens28 presents a number of design challenges. First, this requires thatlens 28 is in close proximity to quantum cascade laser 14. In the '806patent, this is accomplished by placing lens 28 and lens supportstructures 35 inside box 12 adding to the challenges of designing andmanufacturing box 12.

This in turn requires positioning lens 28 with a high degree of accuracyrelative to quantum cascade laser 14. The '806 patent seeks to meet thisrequirement by utilizing the heat spreader 18 as an optical platform,noting that “[t]he output lens . . . and laser gain medium . . . areheld in a secured, fixed and rigid relationship to one another by virtueof being fixed to the optical platform. The use of the heat spreader . .. as a monolithic support block for both lens . . . and laser gainmedium . . . is said to be among “other factors contributing to thesmall footprint include the monolithic design of the various elements,particularly as related to the positioning of the optical components andthe ability to efficiently remove the large amount of heat from the QCLserving as the laser gain medium.

The '806 patent also describes positioning heat spreader 18 onthermoelectric cooling system 26 and the thermoelectric cooling system26 in turn is positioned on a surface that can transfer heat from box12. Thermoelectric cooling system 26 is used to ensure that heatspreader 18 maintains a temperature where heat spreader 18 holds theoutput lens 28 and laser gain medium 14 are held in the secured, fixedand rigid relationship.

This approach requires an increase in the size of thermoelectric coolingsystem 26, an increase in the thermal mass that must be cooled bythermoelectric cooling system 26 and a concomitant increase in theamount of energy that will be consumed by thermoelectric cooling system26 during use. This, in turn, reduces the overall efficiency of a laserdevice that uses high heat load laser module 10, and increases theweight and size of portable power supplies that must be provided in alaser device that incorporates high heat load laser module 10.

Additionally, limitations on the size and position of lens 28 can limitthe ability of lens 28 to reduce the divergence of the mid-wave orlong-wave infrared light emitted by quantum cascade laser 14. Thus,where it is desirable that a laser device that uses high heat load lasermodule 10 provides a collimated beam additional focusing optics outsideof high heat load laser module 10 are generally needed. This, in turn,requires that a laser device that uses high heat load laser module 10provide additional optical elements and mounting structures. Theadditional optical elements and mounting structures further increase thevolume, weight, complexity, and cost of the laser device whileintroducing additional vectors through which the reliability andruggedness of the laser device may be reduced.

As is also shown in FIGS. 1 and 2, high heat load laser module 10includes a plurality of electrical conductors 30 that project fromsidewalls 42 and 44. As is apparent from FIG. 2, the use of side wallprojecting electrical conductors 30 in high heat load laser module 12causes high heat load laser module 12 to have a significant crosssectional area causing a laser device that incorporates high heat loadlaser module 12 to have an even larger cross sectional area.

For example, as is shown in FIG. 2, a laser device that is toincorporate high heat load laser module 12 in, for example, acylindrical package, will have a minimum theoretical radius 48. However,in application a laser device that uses high heat load laser module 12will be required to provide connectors (not shown) that connect to endsof conductors 30 and therefore will have a larger required radius toaccommodate laterally joined connectors. Further, to the extent that itis desired to enclose the connectors and the laser module, such anenclosure will add additional radius and cross sectional area.

Smaller high heat load laser modules are known. For example the DFB-CWtype quantum cascade lasers sold by Hamamatsu Corporation, Japan includeconductors that project from one or the other of sidewalls of a box,however the size enhancing effects of side projecting conductors areonly partially ameliorated by this approach.

Another concern with the high heat load laser module 12 is that highheat load laser modules 12 are highly specialized designs that areintended for specific purposes and that do not easily allow modificationand repurposing. Accordingly any use of such a module for anotherpurpose requires adaptive electronics, hardware and optics, whichincrease the cost, size, weight and complexity of a laser emittingproduct.

It will be appreciated from this that other approaches are needed.

One alternative approach is shown in German patent publication numberDE10205301A1, filed on Feb. 2, 2002. FIG. 3 is a side view of a laserdevice adapted from the '301 publication. This patent publicationdescribes the use of a laser device 50 having a quantum cascade laserLED 52 that is contained between a base section 54 and a housing section58. Electrical conductors pass through base 54 and extend along an axis60 in a first direction, while quantum cascade laser 52 is arranged on apedestal 56 on base 54 to emit light generally along axis 60 in a seconddirection.

In one embodiment, housing 58 has a front wall section 62 with anopening 64 through which radiation from quantum cascade laser 54 canpass. A lens 66, preferably a Fresnel lens, is inserted the opening 64.Lens 66 collimates a light emitted by quantum cascade laser 54 to form abeam. As is described in the '301 application, a distance d separatesthe quantum cascade laser 54 and lens 66. To achieve desired collimationthe distance d is equal to a focal length of lens 66.

Another laser module design has been proposed in US Pat. App. No.2005/0008049 entitled “optical module including a Peltier device thereinand having a coaxial type package” filed by Oomori et al. on Jun. 2,2004.

FIG. 4 shows a cutaway portion isometric view of a co-axial laser module70 and adapted from the '049 application and FIG. 5 shows an end view oflaser module 70. As is shown in FIGS. 4 and 5 conductors 72 arepositioned on one side of a base 74 and a semiconductor diode laser 76is positioned on the opposite side of base 74 and enclosed by a housing78. An opening 82 is provided in housing 78 to provide a light path outof housing 78 and a lens 84 is positioned in opening 82 to reduce theextent of the divergence of light emitted by semiconductor diode laser76.

This approach attempts to solve some of the aforementioned problems byproviding a thermo-electric cooler 86 between base 74 and housing 78 andassembling a support 88 for a semiconductor diode laser 76 ontothermoelectric cooler 86 to provide a shorter path for heat transferbetween semiconductor diode laser 76 and thermoelectric cooler(described as a Peltier device) 86.

However, this approach makes the process of designing a laser module ina coaxial design more challenging by requiring the installation ofthermoelectric cooler 84 within the coaxial package, the connection ofadditional electrical connectors to thermoelectric cooler 86, themounting of a stem at an angle that is normal to the mounting surface onthermoelectric cooler 86, and the mounting of a semiconductor laserdiode to support 88 at an angle that is normal to support 88. Further,this approach limits the overall size and thermal managementcapabilities of the thermoelectric cooler 84.

Still another approach to providing an alternative to a high heat loadpackage is described in U.S. Pat. No. 8,442,081 entitled “QuantumCascade Laser Suitable for Portable Applications” filed on Apr. 25,2012. This describes a laser device with a lens system at a first endthat emits collimated infrared light and a cap at a second end. Aquantum cascade laser directs divergent laser light toward the lens. Acontrol circuit and a battery storage area are positioned between thequantum cascade laser and the cap. Heat from the quantum cascade laserpasses from the quantum cascade laser through a heat spreader providingwhat is described as a short path to a laser housing to provide alimited amount of passive cooling. A drive circuit operates the quantumcascade laser at a low duty cycle to limit the amount of heat generatedby the quantum cascade laser to an amount that can be dissipated by thelimited amount of passive cooling.

Effectively the package described in the '081 patent offers a designer asimple tradeoff: forgo the problems associated with the use of athermoelectric cooling device at the cost of limiting laser use to alevel only generates so much heat as can be passively dissipated by thelaser system.

Additionally, it will be appreciated that, the use of laser modulehousings to position lens systems as is shown in the '301 publication,the '049 application and the '081 patent imposes a number of constraintson the design of the laser module. For example, the laser module housingmust be designed and assembled so that the lens is held in opticalalignment with the quantum cascade laser that is supported on the baseand is separated from the quantum cascade laser by the focal distance ofthe lens. Additionally, the housing and the lens must be designed andassembled such that the relative alignment and positioning of the lensand the quantum cascade laser do not change because of changing thermalconditions that arise during operation laser or changing environmentalconditions.

Similarly, positioning a lens at an opening of a laser module housingplaces many constraints on the optical properties of the lens and themountings used to join the lens to the housing. For example,cross-sectional area constraints housing, volume constraints of thehousing, as well as mechanical and thermal properties of the housingwill impose limitations on the size and shape of the lens.

Another challenge that must be met when the lens is placed in theopening of a laser module housing arises when the laser module is toform part of a hermetic or other seal to provide a controlledenvironment around the quantum cascade laser. For example, in some casesit can be advantageous to operate the quantum cascade laser in a lowpressure or vacuum environment or to operate the quantum cascade laserin the presence of inert gasses or even to simply limit the humidity inthe environment about the quantum cascade laser. Where it is beneficialto provide such controlled environments within a laser module, a seal,typically a hermetic seal is required and it is necessary that both thelens and lens mounting are designed and assembled to operate as afunction of the seal. However, it is also necessary that the opticalfunctions of the lens and the lens mounting are not compromised byincorporating the lens and the mounting into the design of the housing.

This requires new and innovative approaches to providing lens mountings,lens designs and assembly processes that can be efficiently used toestablish an effective seal while also allowing the lens to bepositioned at a precise optical alignment and relative position to thequantum cascade laser.

It will be understood that these design challenges are not easily met.Accordingly, what is still needed in the art is a new laser modulepackage with reduced cross-sectional area requirements, reduced volumerequirements, reduced weight, greater efficiency, reduced complexity,greater ease of manufacturability, increased portability, greaterresistance to shock, vibration, tension, compression, and bending,thermal variations, and environmental conditions.

As is noted above, there are many possible applications for solid statelasers. These applications typically have different performancerequirements including but not limited to different laser coherence,divergence, output powers, ruggedness and portability requirements,efficiencies, intensities and wavelengths. Accordingly, each differentapplication may have other specialized optical, mechanical or electricalfeatures. When such systems are packaged with lenses that are internalto or otherwise joined to a laser housing there is an inherent linkagebetween the laser used and the system requiring redesign of the entiremodule for each compact laser/lens solution.

What are needed therefore, are laser systems and laser modules for usein laser systems that are smaller, lighter more compact and less complexwithout introducing the reliability, design, and manufacturingcomplexities.

BRIEF SUMMARY OF THE INVENTION

In aspects of the invention, optical systems are provided for asemiconductor laser that emits a divergent laser light. In one example,the optical system has a lens with a focal length of greater than 10 mmand that can collimate the divergent laser light into a collimated beamhaving less than a predetermined divergence when the lens is positionedwithin a larger range of positions about a focal length of the lens;and, a frame is assembled to the lens to hold the lens within the largerrange of positions when the system is in a first range of temperature.The larger range of positions is at least 50 percent greater than asmaller range of positions that an alternate smaller lens having a samenumerical aperture as the lens and smaller focal length can bepositioned within to provide a collimated beam having less than thepredetermined divergence.

In other aspects of the invention, laser systems are provided having anenclosure having a front wall with a window therein and a back wall fromwhich a header extends; a semiconductor laser positioned on the headerto direct a divergent laser light through the window; a lens with afocal length of greater than 10 millimeters, and that can collimate thedivergent laser light into a collimated beam having less than apredetermined divergence when the lens is positioned within a range ofpositions about a focal length of the lens; and, a frame assembled tothe lens to hold the lens apart from the semiconductor laser at or aboutthe focal length of the lens over a range of temperature. A drivecircuit links a power supply to the semiconductor laser, and a housingholds the drive circuit, the power supply, the enclosure, the lens andthe frame so that the collimated laser beam emits from the housing. Therange of positions is at least 50 percent greater than a second range ofpositions that an alternate lens having a same numerical aperture as thelens and a diameter of less than about 10 mm can be positioned within toprovide a collimated beam having less than the predetermined divergence.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 shows an exploded isometric view of a prior art high heat loadlaser module package;

FIG. 2 shows a front assembled elevation view of the high heat loadlaser module package of FIG. 1

FIG. 3 shows an example of a prior art laser module presenting analternative to the high heat load laser module package of FIGS. 1 and 2.

FIG. 4 shows a side isometric view of an example of a prior art lasermodule presenting an alternative to the high heat load laser modulepackage.

FIG. 5 shows a front elevation view of the prior art laser module ofFIG. 4.

FIG. 6 is a schematic view of a first embodiment of a laser deviceaccording to a first embodiment of the invention.

FIG. 7 is a top view of one embodiment of a laser system according tothe embodiment of FIG. 6.

FIG. 8 is an end view of the embodiment of FIG. 7.

FIG. 9 is cross-section view of one embodiment of a laser module.

FIG. 10 illustrates the operation of a laser module having an embodimentof an athermalized frame.

FIG. 11 illustrates the operation of a laser module having an embodimentof an athermalized frame.

FIG. 12 illustrates the operation of a laser module having an embodimentof an athermalized frame.

FIG. 13A illustrates an embodiment of one embodiment of a lens.

FIG. 13B illustrates an embodiment of an alternative smaller focallength lens of the prior art.

FIG. 14 is an X-Y chart depicting a first plot of the divergence of abeam from lens and a second plot of the divergence of a beam fromsmaller focal length lens when lens and smaller focal length lens areexposed to identical divergent beams of infrared laser light from asemiconductor laser.

FIG. 15 illustrates an embodiment of a laser system that provides anoptional thermoelectric cooling system.

FIG. 16 is a cross-section view of another embodiment of a laser module.

FIG. 17 is a cross-section view of the embodiment of FIG. 16.

FIG. 18 is a cross-section partial view of an embodiment of a lasermodule.

FIG. 19 is an end view of the embodiment of FIG. 18.

FIG. 20 is a cross-section partial view of an embodiment of a lasermodule.

FIG. 21 is an end view of the embodiment of FIG. 20.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 6 is a schematic view of first embodiment of a laser system 100.FIGS. 7 and 8 illustrate respectively top and end views of theembodiment FIG. 6. In the embodiment illustrated in FIGS. 6-8, lasersystem 100 has a system housing 102 that encompasses, substantiallyencloses, or otherwise retains, a laser module 104, a drive circuit 106,a system controller 108, a user input system 110, sensors 112, a useroutput system 114, a communication system 116, and a power supply 118.

In this embodiment, system controller 108 receives signals from userinput system 110, sensors 112, and communication system 116 anddetermines whether a response to such signals is required. When systemcontroller 108 determines to respond to received signals by causing alaser emission, system controller 108 sends signals to drive circuit 106causing drive circuit 106 to supply electrical energy from power supply118 to laser module 104 in a manner that causes laser module 104 to emita beam of collimated laser light 122. System controller 108 can alsogenerate signals that cause user output system 114 to generate a humanperceptible output. Additionally, system controller 108 can send signalsto communication system 116 causing communication system 116 to send orother signals to other devices and can receive signals fromcommunication system 116 from other devices. Power supply 118 provideselectrical energy to drive circuit 106, control system 108, user inputsystem 110, sensors 112, user output system 114, and communicationsystem 116. Accordingly, system housing 102 encloses a stand-alonedevice capable of laser emission.

System housing 102 can be formed of any of a variety of rigid materialssuch as composites, laminates, plastics or metals. In one configuration,system housing 102 can be formed of an extruded aluminum, therebyproviding sufficient strength without requiring significant weight whilealso providing good thermal transfer properties.

System housing 102 can be fabricated or assembled in any of a variety ofways. In one embodiment system housing 102 is machined such as by EDM(electrical discharge machining), assembled, or molded if composites,laminates, plastics or metals are employed for system housing 102.System housing 102 also can be fabricated using other conventionaltechniques including but not limited to additive assembly techniques.

In FIGS. 6-8, system housing 102 is shown having a generally cylindricalprofile. However, in other exemplary embodiments, system housing 102 maybe configured to mount to any of a variety of direct fire weapons suchas handheld, side, and small firearms. Such firearms include, but arenot limited to, pistols, rifles, shotguns, automatic arms,semi-automatic arms, rocket launchers and select grenade launchers andbows. In other embodiments, system housing 102 can be configured tomount any known dismounted or dismounted crew-served weapon, such asmachine guns, recoilless rifles and other types of crew served weapons.In still other embodiments, system housing 102 can be shaped, sized orotherwise provided in forms that more readily interface with any of avariety of clamping or mounting mechanisms such as a Weaver-style orPicatinny rail or dove tail engagement for mounting to these firearms.

In other exemplary embodiments, system housing 102 can be configured asa component part of a firearm or other direct fire weapon, such as aforegrip, sight or stock.

Drive circuit 106 receives power from power supply 118 and controlinputs from system controller 108. In response to the control inputsreceived from system controller 108, drive circuit 106 generates signalsthat cause laser module 104 to emit laser light. In the embodiment thatis illustrated in FIG. 6 laser module 104 is not directly connected topower supply 118 but rather receives power by way of drive circuit 106such that drive circuit 106 can control the time, duration, andintensity of electrical energy supplied to laser module 104. Drivecircuit 106 may be configured to assist in tuning and/or otherwisecontrolling the output of laser module 104. Drive circuit 106 can beconstructed to provide either pulsed or continuous operation of lasermodule 104. The rise/fall time of the pulse, compliance voltage andcurrent generated by drive circuit 106 for the laser module 104 areselected to minimize power consumption and heat generation whileachieving a desired beam intensity. These parameters may also beselected to cause laser module 104 to produce a beam having a desirablewavelength, frequency, and/or other quantifiable characteristics.

Depending on the desired output, drive circuit 106 can enable operationof the laser module 104 as a continuous or pulsed laser, such as bypassive, active, or controlled switching. Although specific valuesdepend upon the particular laser module 104 and intended operatingparameters, it is contemplated the peak power draw of drive circuit 106may be between approximately 1 amp and approximately 10 amps, with anaverage current draw between approximately 0.1 amps and approximately1.0 amps. As the required voltage may be between on averageapproximately 9 volts and approximately 12 volts, approximately 0.9 W toapproximately 12 W may be consumed. This may represent a substantialpower consumption as well as heat generation.

In an exemplary embodiment, drive circuit 106 may assist in controllingand/or modifying the power level of laser module 104 to aid inpenetrating components or conditions of the atmosphere through whichlaser system 100 will direct beam 122. Such components or conditions mayinclude, for example, snow, rain, fog, smoke, mist, clouds, wind, dust,gas, sand, and/or other known atmospheric or airborne components. Forexample, drive circuit 106 can be configured to controllably, manually,and/or automatically increase the current and/or voltage directed tostrengthen and/or intensify beam 122 emitted by laser module 104 in suchconditions.

It is also understood that laser module 104 can have more than onesemiconductor laser 180. In one exemplary embodiment of this type, alaser module 104 can have one semiconductor laser 180 in the form of amid-range adapted infrared quantum cascade laser and anothersemiconductor laser 180 in the form of a long-range adapted infraredquantum cascade laser. Other combinations of semiconductor lasers 180are possible.

Alternatively, in other embodiments, laser module 104 can includecomponents that can receive signals from drive circuit 106 and that canadjust power supplied to laser module 104 in response to such signals.In such an alternative embodiment, laser module 104 may receive mayreceive electrical energy directly from power supply 118.

In the embodiment illustrated in FIGS. 6-8 system housing 102 hasplurality of openings shown as openings 120, 124, 126 and 128. Incertain embodiments, seals 140, 142, 144, 146 can be supplied to providea barrier to resist entry of contaminants at openings 120, 124, 126 and128 so as to protect the components disposed within system housing 102from water, dust, vapors, or other harmful contaminants commonlyexperienced in non-controlled environment use. Optionally, systemhousing 102 can be hermetically sealed, at least in part around lasermodule 104.

User input system 110 includes human operable sensors such as switches,touch pads, joysticks, audio, video, keypads, key locks, proximitysensors or any other known types of sensors that can detect a user inputaction and that can provide signals to system controller 108 indicativeof the user input action. In the embodiment of FIGS. 6-8, user inputsystem 110 provides a switch 130 that takes the form of a four positionmode switch with different settings to enable manual selection of threedifferent operating mode selections and an off selection.

Sensors 112 can include any form of device that can be used to detect orotherwise sense conditions inside or outside of system housing 102 thatmay be useful to system controller 108 in determining actions to betaken in operating laser system 100. Sensors 112 can include withoutlimitation, light sensors such as photovoltaic cells, contact switches,opto-electronic sensors such as light beam emitter and sensor pairs,electro-mechanical sensors such as limit switches, strain sensors, andproximity sensors such as Hall effect sensors, thermal sensors,meteorological sensors, such as humidity sensors, accelerometers,orientation sensors and other known sensors and transducers.

User output system 114 can include, without limitation actuators, lightemitters, video displays, or other sources of human perceptible visual,audio or tactile signals from which a user can determine for example,and without limitation, a status of laser system 100, an operating modeof laser system 100, or that laser system 100 is emitting a laser beam122 and a characteristics of the laser beam 122 that laser system 100 isemitting or will emit when instructed to do so. In this embodiment, useroutput system 114 includes a video display 132 that is positioned inopening 128.

Communication system 116 can include any combination of knowncommunication circuits including wired or wireless transponders,transceivers, transmitters, receivers, antennas, modulators,de-modulators, encryption and de-encryption circuits or software and canprovide other known components to facilitate data communication, theexchange of control signals or power exchanges in wired or wirelessform.

Power supply 118 is shown located within system housing 102. In oneconfiguration, power supply 118 comprises a battery and system housing102 can include a battery compartment (not shown) sized to operablyreceive and retain a power supply 118 in the form of batteries.Depending upon the anticipated power requirements, available space, andweight restrictions, the batteries can be N-type batteries or AA or AAAbatteries. Additionally, a lithium/manganese dioxide battery such asmilitary battery BA-5390/U, manufactured by Ultralife Batteries Inc. ofNewark, N.Y. can be used with laser system 100. The battery-type powersupply can be disposable or rechargeable. Battery compartment can beformed of a weather resistant, resilient material such as plastic, andshaped to include receptacles for receiving one or more batteries orother power storage devices. Further, the battery compartment may beselectively closeable or sealable to prevent environmental migrationinto the compartment or to create a hermetically sealed environmenttherein.

In other exemplary embodiments, power supply 118 can take the form of afuel cell, capacitive system or other portable electrical energy storageor generation system. It is understood that any type of power supply118, preferably portable and sufficiently small in size can be utilized.

As is noted above, system controller 108 drives operation of lasersystem 100 and receives signals from user input system 110, sensors 112and communication system 116 that system controller 108 can use tocontrol operation of laser system 100. System controller 108 comprisefor example a computer, a microprocessor, micro-controller, programmableanalog logic device or a combination of programmable or hardwiredelectronic devices capable of performing the functions and actionsdescribed or claimed herein.

In the embodiment of FIGS. 6-8, system controller 108 determines a modeof operation of laser system 100 in response to a position of switch130. When switch 130 is positioned in the “Off” position, user inputsystem 110 sends signals to controller 108 causing system controller 108to remain in an inactive state or can maintain a low power consumptionmode of operation.

However, when system controller 108 receives signals from user inputsystem 110 indicating that switch 130 has been moved to the “On”position system controller 108 can generate signals causing drivecircuit 106 to drive laser module 104 to generate laser light. In otherembodiments, switch 130 can comprise a switch that provides power toinitiate operation of system controller 108 only when switch 130 is in aposition other than the “Off” position.

Other modes of operation are possible. For example a “Stand By” mode ofoperation can be provided to conserve stored energy of from power supply118 while maintaining the laser system 100 in an advanced state ofreadiness for use. For example, when sensor 130 is moved to the “StandBy” position user input system 110 can send signals to system controller108 from which controller 108 can determine that this mode of operationhas been selected.

In one embodiment, system controller 108 can detect that switch 130 hasbeen moved to the “Stand By” position and can respond to this by sendingsignals to drive circuit 106 causing drive circuit 106 to beginsupplying power circuits or subsystems, if any, that require some timeto reach a state where they are ready for immediate activation whenswitch 130 is moved to the “On” position. Not all circuits or subsystemswill need be activated at such times and a stand by option relieves theoperator from being confronted with the choice of operating the lasersystem 100 in a high power consumption “On” mode prior to the need to doso and the choice of holding the device in the “Off” state to conservepower with the understanding that there will be a lag time beforeactivation.

Additionally, in the embodiment of FIGS. 6-8 switch 130 can bepositioned at a location that indicates that laser system 100 is to beoperated in a “Test” mode. In one example of this type system controller108 can cause laser module to emit a lower powered laser beam 122. Thislower powered laser beam can 122 be used to allow verification of theoperational status of laser system 100 such as by emitting a lowerpowered laser test beam that can be directed at, for example, nearbytargets for training purposes or at target strips or pages that changein appearance when illuminated by the laser in the test mode. Here too,this mode will be entered when system controller 108 receives a signalfrom user input system 110 indicating that switch 130 has been moved toa position selecting the “Test” mode.

Turning now to FIG. 9 what is shown is a cross-section schematic view ofone embodiment of a laser module 104. In the embodiment that isillustrated in FIG. 9, laser module 104 has an enclosure 150 with a base152 having a front side 154 from which a header 156 extends in a firstdirection 160 and a housing 170 shaped to combine with front side 154 toform a sealed environment about header 156.

A semiconductor laser 180 is mounted to header 156. In this embodiment,semiconductor laser 180 is mounted to header 156 by way of a submount182 and is positioned to direct a divergent laser beam 184 in firstdirection 160 through a window 172 on a front portion 174 of housing170. Semi-conductor laser 180 or submount 182 can be joined to header156 in any of a variety of ways including conventional fasteners,solders, conductive adhesives and the like. Semiconductor laser 180 inturn is typically bound to submount 182 using soldering techniques,although other techniques are also known.

Semiconductor laser 180 can comprise for example, any semiconductordevice that can emit a laser output. Examples of semiconductor laser 180include but are not limited to a diode laser, quantum cascade lasers,inter-band cascade lasers. These types of semiconductor lasers 180 sharegenerally the characteristics of being made from a semiconductormaterial and having a emitting a divergent laser light beam while alsogenerating a meaningful amount of heat that must be dissipated toprotect semiconductor laser 180.

In the embodiment illustrated in FIG. 9, semiconductor laser 180 emits adivergent laser light 184 having a wavelength in the infrared regionsuch as between 2μ and 30μ wavelength. However, in other embodiments,semiconductor laser 180 can emit a divergent laser light 184 having anyof a wide range of wavelengths including but not limited to ultravioletwavelengths, visible wavelengths, and near infrared wavelengths. For thepurposes of the following discussion, it will be assumed that in theembodiment of FIG. 9, semi-conductor laser 180 is a quantum cascade typelaser.

In the embodiment shown in FIG. 9, a plurality of conductors 190 a and190 b are connected at first ends 192 a and 192 b thereof tosemiconductor laser 180 by way of individual wire bonds 194 a and 194 b.Conductors 190 a and 190 b pass through base 152 through non-conductivesealed openings 196 a and 196 b in base 152 and extend in a seconddirection 164 that is opposite first direction 160.

It will be appreciated that in some embodiments different number ofconductors 190 can be used. Typically, each conductor 190 has at leastone wire bond 194 that is used to supply power to heat emitting laser180. For the purposes of clarity, only two are shown here. In otherembodiments, more than one conductor 190 may be used. Additionalconnectors may be used to allow signals to pass to and from componentswithin the enclosure formed by base 152, housing 170 and window 172.This can be used for example to allow drive circuit 106 or systemcontroller 108 receive signals from a sensing device such as athermistor or other heat sensor or a photosensor so that driver circuit106 or controller 108 can determine the temperature near semiconductorlaser 180 or the light output of semiconductor laser in order to enablefeedback/control purposes. In still other embodiments, additionalconductors 192 can be used as necessary to provide additional sensing,control, or power paths into and out of the enclosure made between base152, housing 170 and window 172.

A frame 200 is joined to base 152 and extends from base 152 past window172 to position a lens 210 at a distance along axis 162 fromsemiconductor laser 180. In operation, semiconductor laser 180 generatesa divergent laser beam 184 which is directed toward lens 210. Lens 210collimates the divergent laser beam 184 from laser 180 into a collimatedlaser beam 122 when positioned at a location where lens 210 caneffectively focus light from laser 180. As used herein a collimatedlaser beam 122 includes a laser beam that is fully collimated as well aslaser beams having substantial collimation with a limited allowabledivergence.

In general, lens 210 can provide a high degree of collimation ofdivergent laser light if held at its focal distance from semiconductorlaser 180. However, in practical use this is difficult to achieve with astatic lens mounting design. In particular it will be understood that avariety of forces can conspire to influence the distance that amechanical system such as frame 200 will position lens 210. Chief amongthese are the forces of thermal expansion and contraction which cancause significant changes in the length of components of frame 200 andthe resultant position of lens 210 relative to semiconductor laser 180.

Accordingly, frame 200 is of an athermalized design meaning that frame200 is designed so that frame 200 will hold lens 210 in a desirablerange of positions relative to semiconductor laser 180 despite anythermal expansion or contraction of any components of frame 200 that mayarise during transport and operation of laser system 180. Such systemsdo not seek to completely resist or prevent heating or cooling of frame200, but rather are defined to provide mechanisms to allow for automaticcompensation for any thermal expansion caused by such heating orcooling.

FIGS. 10-12 illustrate the operation of a laser module 104 having anembodiment of an athermalized frame 200. As is shown in these FIGS.10-12 frame 200 is provided in segments that are positioned, anchoredand/or linked to allow thermal expansion of materials in frame 200 butthat are arranged so that different segments of frame 200 createoffsetting effects when exposed to a given thermal stimulus.

As is shown in FIG. 10, frame 200 has first frame segments 250 and 252having anchor ends 254 and 256 and movable ends 258 and 260,respectively. To simplify the following discussion it will be assumedthat first frame segments 250 and 252 are formed from materials having acommon coefficient of thermal expansion and are shaped and assembled ina common manner so that a common distance is between base mounting ends254 and 256 and movable ends 258 and 260, respectively at any giventemperature level. However, in other embodiments these characteristicsof first frame sections 250 and 252 can vary according to the needs ofsuch embodiments.

In the embodiment that is illustrated in FIG. 10, base mounting ends 254and 256 are shown connected directly to base 152. In other embodiments,base mounting ends 254 and 256 can be connected to base 152 by way ofintermediate structures such as system housing 102 or other structuresnot shown including but not limited to a heat spreader or athermoelectric cooler.

As is also shown in FIG. 10, frame 200 has second frame sections 270 and272 having frame mounted ends 274 and 276 and lens movable mountings 278and 280, respectively. To simplify the following discussion it will beassumed that second frame sections 270 and 272 are formed from materialshaving a common coefficient of thermal expansion and are shaped andassembled in a common manner so that a common distance is between framemounted ends 274 and 276 and lens mounted ends 278 and 280 respectivelyat any given temperature level. However, in other embodimentscharacteristics of second frame sections 270 and 272 can vary accordingto the needs of such embodiments.

FIG. 10 illustrates frame 200 at a nominal temperature. It will beappreciated from FIG. 10 that first frame segments 250 and 252 arearranged in a first direction 160 extending away from base 152 alongaxis 162 by a distance F1. Second sections 270 and 272 have framemounted ends 274 and 276 that extend therefrom in second direction 164to lens mountings 278 and 280 by a distance F2. Accordingly, theposition of lens 210 is determined in part by the difference between F1and F2 and in this embodiment lens 210 frame segments 250, 252, 270 and272 are defined to hold lens 210 at a focal length of lens 210 fromsemiconductor laser 180 when laser module 104 is at a nominaltemperature.

FIG. 11 illustrates laser module 104, frame 200 and lens 210 at anelevated temperature range. At this elevated temperature range, thedistance F1 is greater by a first thermal expansion distance X. Theamount of first thermal expansion distance X is determined by thedistance F1, a coefficient of thermal expansion first frame segments 250and 252 and a difference in temperature between the nominal temperatureand the elevated temperature. In FIG. 11, thermal expansion of firstframe sections 250 and 252 at movable ends 258 and 260.

However, the distance F2 is also increased by a thermal expansiondistance Y in second direction 164. The thermal expansion distance Y isdetermined by the distance F2, the coefficient of thermal expansion ofsecond frame segments 270 and 272 and the difference in temperaturebetween the nominal temperature and the elevated temperature.

As can be seen in FIG. 11, first frame segments 250 and 252 and secondframe segments 270 and 272 are defined so that at this elevatedtemperature the difference between X and Y is equal. This can be done bydefining the length of along axis 162 of that first segments 250 and 252and second segments 270 and 272 extend and by selecting combinations ofmaterials having coefficients of thermal expansion for use in firstsegments 250 and 252 and second segments 270 and 272 such that thermalexpansion of first segments 250 and 252 will be offset by the thermalexpansion of second segments 270 and 272 at predetermined thermal rangelimits. It will be appreciated that in some embodiments, frame 200operates in a manner that is generally the converse of that illustratedin FIG. 11 when laser module 104 is used in at temperatures that arebelow the nominal temperature of FIG. 10.

This approach can also require that first frame segments 250 and 252 aremade so that they expand in a first direction 160 at a rate that matchesa rate of expansion of second frame segments 270 and 272 over the rangeof temperatures experienced by laser module 104. This is a particularconcern for laser systems 100 that may be called upon to operate inconditions where ambient temperatures are constantly changing or canquickly change over the course of minutes or seconds, such as wherelaser system 100 is used in aircraft which can experience rapid ambienttemperature changes during flight or where laser system 100 is a handheld device that can be carried in the inside of a jacket and thenremoved for use in cold weather.

In such situations, laser system 100 should have a frame 200 that iscapable of rapidly adapting to ambient conditions and the choice ofmaterials for use in frame 200 must consider the rate at which differentsegments of frame 200 will adapt to thermal transitions. This involvesconsideration of the ability of the segments of frame 200 to receive andabsorb thermal energy from the environment. A number of factors caninfluence this. The first is the overall rate at which a material in thesegments of a frame 200 can absorb or release thermal energy in order tocause a change in length. This can be driven by the rate at which amaterial forming a segment can absorb or release heat and by theavailable surface area through which heat can be transferred into or outof the frame segment. For example, some polymeric materials expandsignificantly when heated but only absorb heat at a rate that issubstantially slower for example than metals. Similarly, the extent towhich each frame segment is directly exposed to ambient thermalconditions will influence the rate at which each fame segment heats andthermally expands.

The rate of thermal expansion can also be driven by the mass of materialin each segment that must be heated or cooled to affect a given unit ofchange per unit of time. Frame segments having large material masses,all other things being equal, will require longer heating and expansiontimes than frame segments having lower masses.

In the embodiment illustrated in FIGS. 10 and 11 selection and design offirst frame segments 250 and 252 and second frame segments 270 and 272have been made such that the position of lens 210 can be held with ahigh degree of accuracy over a useful range of temperatures and withoutactive cooling of frame 200.

However, the challenge associated with providing first frame segments250 and 252 and second frame segments 270 and 272 that provideoffsetting expansion distances over a range of temperatures can bedaunting, particularly where there is little time for thermaladjustment. It will be appreciated that in some cases the extent of arange of positions over which a lens can be moved while providing alaser beam having a divergence that is within a predetermined limit willdictate the extent to which various embodiments of such a solution canbe provided in a cost effective, efficient and effective manner.

In the embodiments described above, anchor ends 254 and 256 of frame 200are linked to base 152 directly and at a point along axis 162 that isbehind laser 180. Accordingly, to the extent that thermal expansion cancause materials that form structures between anchor ends 254 and 256 offrame 200 and semiconductor laser 180 to expand, such expansion willalso operate to reduce the relative separation of semiconductor laser180 and lens 210 and can be incorporated into the overallathermalization planning for laser module 104. In some cases this mayallow for a modest reduction in the required length of second framesegments 270 and 272.

In some cases, the materials forming lens 210 may themselves be impactedby temperature. This can occur for example where the refractive index ofmaterials in lens 210 changes as a function of temperature. This canalso occur for example where the shape of lens 210 changes as a functionof temperature. In some cases, both of these effects can occur.

One effect that these changes in lens properties can have is to changethe focal length of lens 210 as a function of temperature. Where thisoccurs, any such changes should be considered in designing frame 200such that athermalization features of frame 200 cause lens 210 to remainin a position where lens 210 can convert divergent laser light 184 intoa laser beam 122 having a predetermined extent of divergence.

FIG. 12 illustrates a further embodiment of a frame 200 havingathermalization features. FIG. 12 illustrates frame 200 at a nominaltemperature. It will be appreciated from FIG. 12 that in this embodimentfirst frame segments 250 and 252 are arranged in a second direction 164extending away from base 152. Second sections 270 and 272 have framemounted ends 274 and 276 that are joined to movable ends 258 and 260 offirst frame segments 250 and 252 and extend therefrom in first direction160 to lens mountings 278 and 280.

Accordingly, the position of lens 210 is determined in part by thedifference between F1 and F2 and in this embodiment lens 210 framesegments 250, 252, 270 and 272 are defined to hold lens 210 at focallength of lens 210 from semiconductor laser 180 when laser system 100 isat a nominal temperature and to expand or contract in response tothermal stimulus such that lens 210 is held to achieve a desiredcollimation of laser light from lens 210.

In some laser systems 100, an advantage of the embodiment of frame 200of FIG. 12 is that a smaller length of laser module 104 is required toextend past laser 180 thus enabling a more compact laser module 104 orlaser system 100.

It will be appreciated from the foregoing that athermalizationstrategies can be particularly useful in helping to achieve improvementsin the performance of laser system 100 by reducing or eliminating theextent to which lens positions varies as a function of temperature.However, it will also be appreciated that with each additional demandplaced on an athermalization system by the optical system, the lasersystem, and the expected use case of the laser system, the morecomplicated and difficult providing an effective athermalized system canbe. Alternatives such as providing climate control capabilities foroptical systems present the additional problems described above.

It is therefore necessary to consider a different approach to thisproblem, one that allows for greater system level tolerance of thesources of system variation. Additionally, is desirable to address theneeds for laser module systems that can be more readily adapted and morereadily incorporated into systems that are adapted for use in specificapplications.

The present inventors have discovered that contrary to the preferencesof the prior art, smaller more portable laser systems can be providedthat advantageously offer that can generate laser beams having a desiredcollimation without resort to the smaller lenses preferred for suchsystems in the prior art.

Accordingly, lens 210 has a focal length of greater than 10 mm.Preferably, lens 210 has a numerical aperture that corresponds to anextent of divergence of the divergent laser light 184 fromsemi-conductor laser 180. For example, a lens 210 for use with a quantumcascade type of semiconductor laser 180 that emits a divergent laserlight 184 can have a numerical aperture of at least 0.6.

FIGS. 13A and 13B illustrate an example embodiment of lens 210 and analternative small focal length lens 211 preferred in the prior art. Inthis example, both lenses have an input side to receive divergent laserlight such as divergent laser light 184 and are intended to provide anoutput beam of infrared light having no more than a threshold level ofdivergence. Additionally, for the purpose of simplifying the followingdiscussion, lens 210 and alternative smaller focal length lens 211 areassumed to have the same numerical aperture.

However, lens 210 and alternative smaller focal length lens 211 differfrom each other in at least two respects, lens 210 has a larger focallength LFL that for the purposes of the following discussion is twicethe smaller focal length SFL of alternative smaller focal length lens211 and lens 210 has a larger lens diameter LLD that is twice thediameter of a smaller lens diameter SLD of alternative smaller focallength lens 211.

FIG. 14 is an X-Y chart depicting a first plot 220 of the divergence ofa beam from lens 210 and a second plot 222 of the divergence of a beamfrom smaller focal length lens 211 when lens 210 and smaller focallength lens 211 are exposed to identical divergent beams of infraredlaser light 184 from a semiconductor laser 180. In the chart of FIG. 14,plots 220 and 222 are plotted with reference to a Y-axis representing anextent of divergence in a beam exiting from larger lens 210 and smallerfocal length lens 210 and with reference to an X-axis representingpositions of larger lens 210 and alternative smaller focal length lens211 relative their respective focal lengths.

In FIG. 14, the intersection of first plot 220 with centerline 226represents the divergence of a beam of infrared light emitted by lens210 when lens 210 is separated from the quantum cascade typesemiconductor laser 180 by the larger focal length LFL. Similarly, theintersection of second plot 222 with centerline 226 representsdivergence of the beam exiting from smaller focal length lens 211 whensmaller focal length lens 211 is separated from a semi-conductor laser180 by the smaller focal length SFL.

As can be seen from the intersection of first plot 220 with centerline226, when smaller focal length lens 211 is positioned apart fromsemiconductor laser 180 by smaller focal length SFL, smaller focallength lens 211 focuses the divergent laser light into a beam having alow divergence 232. As can be seen from the intersection of second plot222 with centerline 226, when larger lens 210 is positioned at largerfocal distance LFD from semiconductor laser 180, lens 210 focusesdivergent laser light into a beam having a lower divergence 230.

It will be appreciated from FIG. 14, that even when lens 210 and smallerfocal length lens 211 are positioned at their respective focal distancesrelative to semiconductor laser 180, smaller focal length lens 211 emitsa beam having a greater divergence than the beam emitted by larger lens210. Accordingly, one benefit of lens 210 is that lens 210 is morecapable of generating a beam with lower divergence.

As is shown in plot 222 in FIG. 14, the divergence of the beam fromsmaller focal length lens 211 rapidly increases when smaller focallength lens 211 is moved in ways that cause the distance betweensemiconductor laser 180 and smaller focal length lens 211 to be greaterthan or less than the smaller focal length SFL.

In contrast, as can be seen from plot 220, the divergence of the beamthat is emitted by lens 210 increases at a much more gradual rate whenlarger lens 210 is moved in ways that cause the distance between thequantum cascade laser 180 and lens 210 to be greater than or less thanthe larger focal distance LFD of lens 210.

Assuming, a hypothetical limit 228 on the preferred level of divergenceof a laser beam 122 that is emitted by laser system 122, lens 210 cancollimate divergent laser light 184 into a collimated beam 122 havingless than a predetermined divergence when lens 210 is positioned withina range of positions 236 about larger focal length LFL. In contrast, analternative smaller focal length lens 211 must be held within a smallerrange of positions 234 around smaller focal length SFL.

In the chart of FIG. 14, the larger range of positions 236 is almosttwice the size of a smaller range of positions 234 within which smallerfocal length lens 211 can be positioned while still providing a beamhaving no more than a the preferred level of divergence. In otherembodiments the difference between the sizes of the large range ofpositions and the small range of positions can be larger or smaller thanthe difference illustrated. For example, and without limitation in oneembodiment, the large range of positions 236 can be about 50% largerthan the size of the smaller range of positions 234.

In sum, through the use of a lens 210, having a focal length of greaterthan 10 mm the risk that forces causing variations in the position oflens 210 relative to semiconductor laser 180 will impact the performanceof laser system 100 is substantially lowered as compared to the extentof such risk when smaller focal length lens 211 of the type preferred bythe prior art is used.

Additionally, when designing a laser system 100 using an alternativesmaller focal length lens 211, care must be taken to ensure that smallerfocal length lens 211 is carefully manufactured within the small rangeof positions 234 relative to semiconductor laser 180.

In contrast the use of a lens 210 helps to prevent or reduce many of thenon-thermal causes of lens mis-positioning. For example, lenses 210 canhave diameters on the scale of 20 mm or more and are easier for assemblypersonnel to manipulate and for equipment to handle and therefore can beassembled into a laser system 210 with increased reliability.

A further advantage available in laser system 100 that includes a lens210 is that lens 210 will be positioned at a longer distance from asemi-conductor laser than an alternative smaller focal length lens 211.Accordingly, there is greater opportunity for transient heat that isgenerated by a semiconductor laser 180 to be dissipated before such heatbegins to have a significant impact on lens 210. This reduces thepossibility that thermal gradients will form in lens 210 that aresufficient to distort the shape of lens 210 in ways that introducedivergence into laser beam 122, that steer laser beam 122 away from adesired direction or that introduce other undesirable effects.

Similarly, the use of lens 210 provides a greater opportunity for heatthat is generated by semiconductor laser 180 to be dissipated beforesuch heat can cause significant sufficient thermal expansion ofcomponents of frame 200 to move lens 210 to a position where lens 210can no longer provide the desired extent of collimation of divergentlaser light 184. In part, this greater opportunity arises because of thegreater length of frame 200 all that must be heated to induce asignificant change in the position of lens 210 relative to semiconductorlaser 180 and in part this occurs because there is a greater opportunityfor such heat to be dissipated before changing the length of frame 200.

In other embodiments further advantages are possible. For example, thesize, weight, complexity or cross-sectional area of frame 200 can bereduced through the use of lens 210. In one example of this, at leastone of the size, weight, or cross-sectional area of a frame 200 can bemade lower can be made lower than a respective size, weight, orcross-sectional area of an alternative system housing having analternate frame that holds an alternative lens in the second range ofpositions over first range of temperatures 236.

This can occur for example because an alternative lens frame that canhold an alternative smaller lens within a smaller range of positions andtherefore frame 200 must impose a greater extent of control over theposition of the alternative smaller lens 211. Such additional controlcan in some cases require a larger number of components because such alens frame has components that require more complex interactions such aslens frames that that have multiple interactions between moving parts,or because such an alternative frame must be composed in a manner withmore complex structures or structural interactions to provide muchtighter controls over the extent of expansion.

In still another example, a frame 200 that positions lens 210 so thatframe 200 holds lens 210 within a first range of positions (shown inFIG. 14 as 236 a) of the first range of positions 236 over a first rangeof temperatures may also be capable of holding lens 210 so that frame200 positions lens 210 within a second portion (shown as 236 b in FIG.14) of the first range of positions 236 at temperatures that are higherthan the first range of temperatures.

In contrast an alternative frame facing a similar temperature range willstill be required to position an alternative smaller focal length lens211 within the smaller range of positions 234. Where this occurs, atleast one of the size, weight, complexity or cross sectional area ofsuch an alternative frame must be increased beyond that which is used toconfine the smaller lens within smaller range of positions 234 over thefirst range of temperatures. Accordingly, at least one of the size,weight, complexity or cross-sectional area of a frame 200 will be lowerthan a respective size, weight, complexity or cross-sectional area of analternative frame that holds an alternative small lens 211 in the firstrange of positions 234 over the second range of temperatures.

That is, an alternate frame for an alternative smaller focal length lens211 has a difficult task in confining smaller focal length lens 211within the smaller range of positions 234 over a first temperaturerange. The challenge associated with holding smaller focal length lens211 within the smaller range of positions 234 increases greatly as therange of temperatures over which smaller lens 211 operates increases andplaces additional demands on the frame to be used with the smaller lens211, thereby requiring changes that increase size, complexity, weightand cross sectional area of such an alternative frame to the point whereother options such as actively cooling the frame as is described in the'806 patent or limiting the duty cycle of the laser as is described inthe '094 patent must be considered.

Additionally, in some embodiments, at least one of the size, weight,complexity or cross sectional area of a system housing 102 having aframe positioning larger lens 210 within the larger range of positionsis lower than a respective size, weight, complexity or cross-sectionalarea of an alternative system housing having a frame that holds analternative lens 211 in the smaller range of positions 234 over thefirst range of temperatures.

In other embodiments, the use of lens 210 can reduce power consumptionrequirements for laser system 100. One example of this is illustratedwith reference to FIG. 15 in which an embodiment of laser system 100provides an optional thermoelectric cooling system 105 that is operated,in this embodiment, by drive circuit 106 to limit the extent to whichany heat generated by operation of the semiconductor laser heats frame200 and lens 210. In such embodiments, the duty cycle of thethermoelectric cooling system 105 is lower in a laser system 100 havinglens 210 than in an alternate laser system having alternate smallerfocal length lens 211 during an equivalent amount of laser usage. Thiscan occur because even small amounts of uncompensated thermal expansionof an alternate frame holding a smaller focal length lens 211 can allowsmaller focal length lens 211 to drift out of second range 234 therebyrequiring a greater level of thermal stability and more usage ofthermoelectric cooling system 105 as compared to an extent of usage ofthermoelectric cooling system 105.

In some embodiments of this type a lower duty cycle of laser system 100having lens 210 places lower power requirements on power supply 118enabling power supply 118 to be smaller than a power supply required bythe lower duty cycle of laser system 100 having lens 210 places lowerpower requirements on the power supply enabling the power supply to besmaller than a power supply in an alternate system having a smallerlaser lens for an equivalent level of laser output.

FIGS. 16-19 illustrate examples of the use of laser modules 104 in lasersystems 100 of FIGS. 6-8. As is shown in a side schematic view in FIG.16 and as a cross-section view in FIG. 17 frame 200 is joined to base152 and first segments 250 and 252 of frame 200 and extends in firstdirection 160 from base 152 and combine with second sections 270 and 272respectively to position lens 210 in the divergent laser light 184 at aposition that causes a laser beam 122 having a limited divergence toemit therefrom. As is shown in FIGS. 16 and 17, in this embodiment base152 and housing 160 are positioned within a cross-sectional area 300 offrame 200 and lens 210.

As is also shown in FIGS. 16 and 17, a plurality of conductors 190extend through base 152 in second direction 164. Conductors 190 provideelectrical connections to allow current to flow through thesemiconductor laser 180. In the embodiment illustrated here, conductors190 extend to driver 106 which operates generally as described above tosupply electrical energy that causes divergent laser light 184 to beemitted and focused into laser beam 122 by lens 210.

Base 152 and housing 170 are sized and positioned for location within across sectional profile of frame 200 and lens 210 however, base 152 andhousing 170 need not occupy the entire cross-sectional area or even asubstantial proportion thereof. In exemplary embodiments, it issufficient that base 152 and housing 170 are within a cross-sectionalprofile of frame 200 and lens 210. For example, base 152 and housing 170can be sized and positioned for location within a cross-sectionaldiameter that is at least large enough to hold frame 200 and lens 210.

In one embodiment, base 152 and housing 170 are sized and positioned forlocation within a predetermined cross-sectional area having at leastabout 275 sq. mm. In another embodiment, base, housing, the frame andthe lens are frame are sized and positioned within a predeterminedcross-sectional area of between 275 and 600 square millimeters.

As is shown in FIGS. 18 and 19, a laser module 104 such as thatillustrated in FIGS. 16 and 17 can be readily incorporated into a lasersystem 100 that having a cylindrical type system housing 102 as isillustrated general in FIGS. 6-8. In particular it will be understoodthat by arranging components of system 100 in such a linear fashion itbecomes possible to provide a laser housing that advantageously can behand gripped and that has a cross-section that is smaller.

As is shown in FIGS. 20 and 21, cross-sectional perimeter 300 of frame200 can be defined in a variety of cross-section shapes. In thisembodiment, frame 200 is illustrated having a rectangular shape withcurved corners. Other cross sectional perimeter are possible includingbut not limited to polygonal shapes, curvilinear shapes and irregularshapes the size of which is determined by frame 200 and lens 210. Crosssectional perimeter 300 of frame 200 and lens 210 can comprise a polygonor other shape that conforms to an outermost perimeter of frame 200 andlens 210.

It will be appreciated that in various embodiments, semiconductor laser180 may comprise a semiconductor laser that generates a divergent laserlight 184. By positioning a lens 210 so that the divergent laser light184 strikes lens 210 after divergent laser light 184 reaches a largerdiameter or area than an area of an alternative smaller focal lengthlens, the larger beam size of divergent laser light at lens 210 allowslens 210 to generate a collimated laser beam 122 having a lowerdivergence than is possible with an alternative smaller lens 211.

In further exemplary embodiments laser system 100 can be combined withor integrated into other systems including but not limited to thermalviewing systems, surveillance systems, vehicles, robotic equipment,ships and aircraft all of which may be controlled manually or by way ofautomatic or control systems. In still other embodiments system housing102 can be shaped and sized to mount to any of a variety of manned orunmanned vehicles used in surveillance, law enforcement, reconnaissance,target marking, friendly force marking, or combat applications. Inexemplary embodiments, such vehicles can include, but are not limitedto, any unattended ground sensors, self-righting camera balls, and otherlike portable devices.

In such exemplary embodiments, any and/or all components of laser system100 may be integrally incorporated into such devices, and in suchembodiments, the system housing 102, or portions thereof, may be omittedif desired. For example, in an embodiment in which laser system 100 isformed integrally with an unmanned ground vehicle, an unmanned aqueousvehicle, a mobile robot, an unattended ground sensor, or other likedevice, the components of the laser module 104 can be hermeticallysealed within such devices and the system housing 102 may be omitted toreduce size, weight, space, power consumption, and/or drag associatedwith laser system 100. In such embodiments, one or more windows, lenses,domes, or other components may be employed proximate to facilitateemission of radiation from laser system 100.

Lens 210 has been shown as a single element lens. This has been done forsimplicity. It will be appreciated that lens 210 can comprise anycombination of optical elements capable of performing the functionsdescribed herein, including but not limited to diffractive or reflectiveelements.

As noted above, embodiments of semiconductor laser 180 can take the formof a quantum cascade laser or an inter-band cascade laser operable toproduce a beam having a wavelength between approximately 1 μm andapproximately 30 μm. In exemplary embodiments, the emitted beam may havea preferred wavelength between approximately 2 μm and approximately 5μm, or between approximately 7 μm and approximately 30 μm. Although asingle solid-state laser is shown in system housing 102, it iscontemplated that a plurality of solid-state lasers 180 can be disposedwithin the system housing 102, some or all of solid-state lasers 180emitting radiation at different respective wavelengths. In additionalexemplary embodiments, a single semiconductor laser 180 can be employedwith an appropriate driver 106 and/or filter to provide a plurality ofcorresponding wavelengths.

Other embodiments of the present disclosure will be apparent to thoseskilled in the art from consideration of the specification and practiceof the various embodiments disclosed herein. It is intended that thespecification and examples be considered as exemplary only, with a truescope and spirit of the present disclosure being indicated by thefollowing claims.

What is claimed is:
 1. An optical system for a semiconductor laser thatemits a divergent laser light, the optical system comprising: a lenswith a focal length of greater than 10 mm and that can collimate thedivergent laser light into a collimated beam having less than apredetermined divergence when the lens is positioned within a largerrange of positions about a focal length of the lens; and, a frameassembled to the lens to hold the lens within the larger range ofpositions when the system is in a first range of temperatures; whereinthe larger range of positions is at least 50 percent greater than asmaller range of positions that an alternate smaller lens having a samenumerical aperture as the lens and smaller focal length can bepositioned within to provide a collimated beam having less than thepredetermined divergence.
 2. The optical system of claim 1, wherein atleast over a portion of the larger range of positions, the lens providesa collimated laser beam having a lower divergence than the alternatesmaller lens can provide when positioned at any position in the smallerrange of positions.
 3. The optical system of claim 1, wherein the framepositions the lens so that the frame holds the lens within a firstportion of the larger range of positions over the first range oftemperatures and wherein the frame allows the lens to be positionedwithin a second portion of the larger range of positions at temperaturesthat are higher than the first range of temperatures.
 4. The opticalsystem of claim 1, wherein at least one of a size, weight, complexity orcross sectional area of the frame is lower than a respective size,weight, complexity or cross-sectional area of an alternate frame thatholds the alternate smaller focal length lens in the smaller range ofpositions over the first range of temperatures.
 5. The optical system ofclaim 1, wherein at least one of a size, weight, complexity or crosssectional area of the frame positioning the lens with in the largerrange of positions is lower than a respective size, weight, complexityor cross-sectional area of an alternate frame that holds the alternatesmaller focal length lens in the smaller range of positions over thefirst range of temperatures.
 6. The optical system of claim 5, whereinat least one of the size, weight, complexity or cross sectional area ofa frame positioning the lens with in the second range positions is lowerthan a respective size, weight, complexity or cross-sectional area of analternative frame that holds an alternative lens in the first range ofpositions over the second range of temperatures.
 7. A laser systemcomprising: an enclosure having a front wall with a window therein and aback wall from which a header extends; a semiconductor laser positionedon the header to direct a divergent laser light through the window; alens with a focal length of greater than 10 millimeters, and that cancollimate the divergent laser light into a collimated beam having lessthan a predetermined divergence when the lens is positioned within arange of positions about a focal length of the lens; and, a frameassembled to the lens to hold the lens apart from the semiconductorlaser at or about the focal length of the lens over a range oftemperatures; a drive circuit linking a power supply to thesemiconductor laser, a housing holding the drive circuit, the powersupply, the enclosure, the lens and the frame so that the collimatedlaser beam emits from the housing; wherein the range of positions is atleast 50 percent greater than a second range of positions that analternate lens having a same numerical aperture as the lens and adiameter of less than about 10 mm can be positioned within to provide acollimated beam having less than the predetermined divergence.
 8. Thelaser system of claim 7, wherein the housing has a cross sectional areaand wherein at least one of a size, weight, or cross-sectional area ofthe housing is lower than a respective size, weight, or cross-sectionalarea of an alternative housing having an alternate frame that holds thealternate smaller lens in the second range of positions over the rangeof temperatures.
 9. The laser system of claim 8, further comprising athermoelectric cooling system operated by the drive circuit to limit theextent to which any heat generated by operation of the semiconductorlaser heats the frame and the lens and wherein a duty cycle of thethermoelectric cooling system is lower in a laser system having the lensthan in an alternate system having the alternate lens during anequivalent amount of semiconductor laser usage.
 10. The laser system ofclaim 9, wherein the lower duty cycle of the system having the lensplaces lower power requirements on the power supply enabling the powersupply to be smaller than a power supply in the alternate system for anequivalent level of laser output.
 11. A laser module comprising: a basewith a front side from which a header extends in a first direction and ahousing shaped to combine with the front side to create a sealedenvironment about the header; a heat generating laser mounted to theheader and directing a divergent laser beam in the first directionthrough a window on a front portion of the housing; a lens shaped toreduce the divergence of the divergent laser beam to a predeterminedlevel and having a focal length of greater than 10 mm; a frame joined tothe base and extending in the first direction from the base past an endwall of the housing to a first side of the lens in the divergent laserbeam so that the lens will emit a laser beam having a limiteddivergence; a plurality of conductors providing electrical connectionsto allow current to flow to the heat generating laser, said conductorsextending through the base in a second direction; wherein the housingand the base are positioned within a cross sectional area of the frameand the lens.
 12. The laser module of claim 11, wherein the enclosureand the base are sized and positioned for location within a crosssectional profile of the frame and the lens the within a cross sectionalprofile of the frame and the lens.
 13. The laser module of claim 11,wherein the housing and the base are sized and positioned for locationwithin a cross-sectional diameter at least large enough to hold the lensand the frame.
 14. The laser module of claim 11, wherein the housing andthe frame are sized and positioned for location within a predeterminedcross-sectional area having of between 275 and 600 square millimeters15. The laser module of claim 11, wherein, the base, the housing, theframe and the lens are sized and positioned within a predeterminedcross-sectional area having at least [should this be “less than”?]275square millimeters.
 16. The laser module of claim 11, wherein the lensis at least about 20 mm in diameter.
 17. The laser module of claim 11,further comprising a cooling system positioned confronting the base andsized and positioned within a cross-sectional profile of the frame andthe lens.
 18. The laser module of claim 11, wherein the base, thehousing, the frame and the lens are arranged relative to a common axis.19. The laser module of claim 11, wherein the heat generating laseremits a divergent laser light having more than one mode and wherein thelens receives the divergent laser light and collimates the divergentlaser light into a collimated beam having less than a predetermineddivergence.